2. Introduction
• The mitochondria (Gr., mito=thread,chondrion=granule) are granular
cytoplasmic organelle
• Are present in all aerobic cells of higher animals and plants and certain
micro-organisms including algae, protozoa and fungi.
• They are absent in bacterial cells
• Vital stain Janus green stains living mitochondria greenish blue due to its
action with cytochrome oxidase
3. Historical
• The mitochondria were first observed by Kolliker in 1850
• And term coined by Benda (1897-1897)
• Altman suggested name bioblast for the mitochondria
4. Distribution or localization
• The distribution and number of mitochondria is depend on functional state
of that cell
• Typically mitochondria with many cristae are associated with mechanical
and osmotic work situations
• More demand of ATP more number of mitochondria. E.g. muscle cells
• Myocardial muscle cells have numerous large mitochondria called
sacrosomes.
• The cells of green plants contain less number of mitochondria than animals
because in plant cells the function of mitochondria is taken over by
chloroplast
5. Biogenesis
• Some theories suggests that mitochondria are originated de novo from the
simple building blocks like amino acids and lipids but there is not direct
evidence
• Fission of mitochondria leads to formation of two new mitochondria
7. Structure
a) Membrane - Mitochondria is bonded by double membrane. The outer
membrane contains many copies of transport protein called porin. Outer
membrane is permeable to all molecules. Inner membrane is impermeable
forming a series of infoldings known as cristae.
b) Oxysomes - also known as inner membrane subunits, elementary particles
F1 particles or f0-F1 particles and are meant for ATP synthesis
(phosphorylation) and also for ATP oxidation (acting as ATP synthetase
and ATPase)
c) Matrix- mitochondria matrix is homogeneous, gel-like proteinaceous
material. Matrix contains lipids, proteins, circular DNA, ribosomes and
granules
8. Chemical composition
• Mitochondria are found to contain 65-70% protein, 25-30% lipids,0.5%
RNA and small amount of DNA.
• Lipid contents of mitochondria are composed 90% phospholipids.
• The inner membrane is rich in cardiolipin (type of phospholipid) which
makes this membrane impermeable
• Mitochondria contains variety of ions like Na, K, Cl, AMP, and so on
9. Chemical composition-Enzymes
I. Enzyme of outer membrane- important enzymes of outer membrane are
monoamine oxidase, NADH-cytochrome C-reductase.
II. Enzymes of intermembrane space- adenylate kinase an nucleotide
diphosphokinase
III. Enzymes of inner membrane- ATP synthetase, cytochrome oxidase and
succinate dehydrogenase
IV. Enzymes of matrix -matrix contains hundreds of enzymes including those
required for oxidation of pyruvate and fatty acids and for citric acid cycle
or Krebs cycle. Contains enzymes like malate dehydrogenase, isocitrate
dehydrogenase, citrate synthetase and so on
10. Function- ATP synthesis
• What is ATP?
• ATP- The adenine and ribose sugar collectively constitute the nucleoside
adenosine, which by having one, two or three phosphate groups forms
AMP, ADP or ATP.
• In ATP last phosphate group is linked with ADP by a special bond known
as energy rich bond. Breakage of this bond releases energy
A P-P-P = A P-P + Pi + 7300 calories
11. Function- ATP synthesis
• Oxidation of carbohydrates
a) Glycolysis- under anaerobic conditions glucose is degraded into lactic acid
by a process of glycolysis (generates 2 ATP)
b) Krebs cycle and ETS- two molecules of FADH2 and 6 molecules of NADH
produced in Krebs cycle (from 2 molecules of acetyl CoA) are oxidised by
molecular o2 in ETS and produces ATP molecules
• Oxidation of fat- during β-oxidation of two molecules of ATP are releases
and total 5 molecules of ATP are produced.
